This invention relates to an improved gas-metal-arc welding method which is particularly useful in out-of-position welding, although it also can be utilized for the flat position. The method is particularly concerned with utilizing a shielding gas formed of a four gas mixture, namely argon and helium with minor amounts of carbon dioxide and oxygen. The welding is performed with a continuous feed, consumable wire electrode gas-shielded-arc welding gun.
This invention is particularly concerned with improvements to a four gas mixture shielded arc, consumable wire welding process earlier invented by John G. Church and disclosed in his U.S. patent application, Ser. No. 404,722 filed Aug. 3, 1982. The general concept of using a four gas mixture was known, having been disclosed, for example, in U.S. Pat. No. 3,139,506 issued June 30, 1964 to Wolff et al, and also, in U.S. Pat. No. 2,907,866 issued Oct. 6, 1959 to Yenni et al and U.S. Pat. No. 2,946,847 issued Aug. 2, 1960 to Craig et al.
Contrasting with the gas mixtures disclosed in the above prior art patents, the Church process focuses upon specific formulation ranges of such gases in the mixture, which have been found to produce unusual and unexpected welding effects. Significantly among these effects are very high melting rates, with corresponding unusually high deposition rates as compared with prior processes. The welds produced have been of superior quality with respect to bead shape, penetration, uniformity, mechanical characteristics such as resistance to brittle fracture, good grain structure, reduced porosity and the like.
The earlier Church process has been utilized with a unique welding gun which is disclosed in the U.S. patent application of John G. Church and Emerson G. Malone, U.S. Ser. No. 349,141 filed Feb. 16, 1982. A consumable wire electrode is fed through a tubular contact tip which is surrounded by a tubular nozzle. The contact tip free end is substantially recessed within the nozzle so that there is an unusually long electrode extension or "stick-out" from the gun contact tip to the end of the electrode where the arc is produced. Roughly half of the electrode extension is recessed within and surrounded by the nozzle. The shielding gas is flowed around the tip and electrode extension, and through the nozzle in a substantially longitudinal laminar pattern. The contact tip is vigorously cooled by conduction due to an external liquid cooling conduit wrapped around the gun end which is remote from the electrode extension.
Consumable wire gas-shielded-arc arc welding guns are known. For example, guns of this type are disclosed in U.S. Pat. No. 3,283,121 issued Nov. 1, 1966 to Barnard et al for an arc welding gun; U.S. Pat. No. 3,469,070 issued Sept. 23, 1969 to Barnard et al for an arc welding gun; and British Patent Specification No. 1,094,008 published Dec. 6, 1967, filed by Linde Aktiengesellschaft in the name of Hildebrandt et al, for gas-shielded-arc welding torches. These disclosures are of different gun constructions utilizing shielding gas flowed around the contact tip, within nozzles and with means for cooling the guns.
The Church process contemplates the deposition of large, molten globules, which are formed on the end of the electrode, by a free-fall or free-flight technique. That is, by application of sufficiently high electrical power to the electrode, large globules of molten material successively form on the end of the electrode, at the arc gap. The globules detach from the electrode and fall into the weld pool or deposit, principally through the effect of gravitational forces.
This free flight transfer is essentially limited to flat position welding, that is, where the arc gap is located below the electrode end. Thus, although a substantial part of commercial welding is done in the flat position, there is a need for adapting the Church process for welding in all positions, that is, particularly for welding in out-of-position, such as overhead welding.